1. Field of the Invention
The present invention relates to the steam turbine used in a power plant such as a nuclear power plant. Further, the present invention relates to the method for operating the steam turbine and the power plant therewith. The present invention especially relates to: the steam turbine into which a vast flow rate of the high pressure steam generated in a nuclear power plant streams; and, the method for operating the steam turbine and the power plant therewith.
2. Background of the Invention
In a nuclear power plant, a nuclear reactor generates steam; the generated steam is supplied to a steam turbine in which a turbine rotor is rotated so that an electric generator coupled to the turbine rotor produces electric power. In general, the high pressure steam generated by the nuclear reactor is fed to a high pressure (steam) turbine of a double flow type as well as to low-pressure (steam) turbines, the low-pressure (steam) turbine being provided as a subsequent stage turbine following the high pressure turbine; or, the high pressure steam generated by the nuclear reactor is fed to a high pressure turbine of a single flow type, an intermediate pressure turbine of a single flow type, and at least one low-pressure turbine, the low-pressure turbine being provided as a subsequent stage turbine following the high pressure turbine and the intermediate pressure turbine.
Incidentally, a steam turbine of a single flow type means a steam turbine in which the working steam streams toward one direction along the rotor shaft; and, a steam turbine of a double flow type means a steam turbine in which the working steam enters the steam turbine from a middle section and streams toward two directions along the rotor shaft (i.e. toward the fore and aft directions along the rotor shaft).
JP1995-332018 discloses a nuclear power plant in which, for example, a high pressure turbine of a double flow type as well as at least one low-pressure turbine is provided, the low-pressure turbine being provided as a subsequent stage turbine following the high pressure turbine. In the disclosed nuclear power plant, the steam generated by the nuclear reactor firstly streams into the high pressure turbine of a double flow type so as to produce mechanical work; then, the steam streams into the low-pressure turbine, after the moisture (mist) of the steam is removed by a moisture separation heater and the steam is heated up by the moisture separation heater.
Further, JP1987-218606 discloses a nuclear power plant in which a high pressure turbine of a single flow type, an intermediate pressure turbine of a single flow type, and at least one low-pressure turbine are provided, the low-pressure turbine being provided as a subsequent stage turbine following the high pressure turbine and the intermediate pressure turbine. In the nuclear power generating system, the steam generated by the nuclear reactor firstly streams into the high pressure turbine of the single flow type so as to produce mechanical work; then, the steam discharged from the high pressure turbine is demisted (i.e. the moisture of the steam is removed) and heated-up by a moisture separation heater; then, the steam enters the intermediate pressure turbine and produces mechanical work; further, the steam is again demisted and heated-up by a moisture separation heater. Subsequently, the steam enters the low-pressure turbine.
Further, JP1995-233704, JP1998-266811, JP2002-508044 and WO1997/30272 disclose the examples of steam turbine plants; each of the turbine plants includes a high pressure turbine of single flow type, an intermediate pressure turbine of a double flow type and a low-pressure turbine as a subsequent stage turbine that follows the high pressure turbine and the intermediate pressure turbine. Hereby, it is noted that the steam turbine plants disclosed by JP1995-233704, JP1998-66811, JP2002-508044 and WO997/30272 disclose are not always for the nuclear power plants,